Ups and Downs
Lab breakthroughs may help us live long in spite of ourselves. But for now, our life span is still heavily influenced by environment and by how well we behave. Some recent findings from the greatest lab of all, the real world:
Breathe easy. Through the 1980s and '90s, U.S. city dwellers gained nearly five months of life expectancy because of clean-air improvements, according to 2009 estimates in the New England Journal of Medicine.
Long life — for some. Americans made solid life-span gains throughout the second half of the 20th century, but not everyone has shared equally. For roughly 4% of the male population and 19% of the female population, according to a 2008 report in the journal PLoS Medicine, life expectancy stagnated or even fell. The main culprits: lifestyle-related diseases like lung cancer and diabetes.
Perils of the plate. If all U.S. adults were normal-weight nonsmokers by 2020, a teenager who turned 18 that year could expect to live an extra 3.76 years, according to Harvard economists and a University of Michigan doctor. But given current trends, the life-span boost from our steadily falling tobacco use may be erased by our steadily rising obesity rates.